User's Manual

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8.2.8 Radio Frequency Interference (RFI)
The system can inadvertently process radio energy as Doppler
speeds, including that from police radios, airport radar, microwave
transmission towers, CB radio transmitters, and AM/ FM
transmission towers . For this type of interference to occur, the
radar unit must be operating very close to the radio transmitter.
The G3™ contains an RFI detection circuit that detects excess radio
frequency energy. When stray radio frequency energy reaches an
excessive level, the system displays the RFI message and stops
processing and displaying speeds. The system resumes normal
operation when the RFI condition no longer exists. At that time,
any locked speeds will display again.
8.2.9 Shadowing
In Moving mode, the radar processes two speeds–patrol and
closing (target). The stronger of the two, the patrol speed, is
created when the radar beam reflects from approaching stationary
objects, such as the pavement or terrain the vehicle is traveling on.
However, some situations cause return signals to be larger than the
reflection from the ground, such as when the patrol vehicle
is rapidly overtaking a slow-moving 18-wheeler. Given a choice
between reading passing ground clutter or the large return signal
generated by the vertical expanse of the truck’s trailer, the radar
might ignore the ground speed and lock onto the stronger return
signal. Rather than receiving a true patrol speed, the radar reads
the differential speed between the vehicle and the 18-wheeler. The
computer then subtracts this artificially low speed from the closing
speed and assigns a higher speed to the target.
The shadowing error is easy to recognize, because the radar
patrol speed and the speedometer reading will vary significantly.
The target speed in this instance also will vary considerably from
your visual estimation. The correct City/Highway setting helps to
minimize this effect.
G3 ™ User & Installation Manual